One of the most challenging problems facing the biorefinery industry is the difficulty of handling and transporting bulk plant based biomass. Typically, these materials must be size reduced before they can be conveniently processed into other valuable products. Pelleting is one of the most common techniques used to convert the ground or loosed materials into more compact, higher density units that are amenable to handling. Pellets can be used as animal feed or they can be used directly in combustion for energy generation. Since the handling properties of pellets are similar to those for grains, existing, well-developed, conventional bulk handling equipment can be used to handle pelleted biomass.
Pelleting normally involves mixing the plant biomass and forcing them through a die to form pellets. More recently, most processors inject steam and binders in order to improve pellet quality and reduce spring back of the biomass as well as reduce wear on the pelleting die cavity. The binder chemical may present problems if the pellet is to be used as animal feed or as an energy source. The chemical binders must receive FDA or CFIA approval before they can be used in feeds. There is currently no effective means of achieving adequate conditioning of the biomass in order to produce high quality pellets. Pellets must be durable and able to withstand the handling operations without breaking.
One chemical component of plant biomass is phytochemicals. Phytochemicals are non-nutritive plant chemicals that have protective or disease preventive properties (Nishino et al., 2005, Oncology, 69: 38-40). There are more than one thousand known phytochemicals. It is well-known that plant produces these chemicals to protect itself but recent research demonstrated that many phytochemicals can protect humans against diseases.
Phytochemicals have been implicated in promoting the function of immune system, act directly against bacteria and viruses, reduce inflammation, and are associated with the treatment and/or prevention of cancer, cardiovascular diseases and many other diseases affecting humans.
Phytochemicals can be regrouped in various families. Terpenoids are largely constituted of carotenoid molecules, which are organic pigments that are naturally occurring in plants. There are over 600 known carotenoids which are divided in two classes: xanthophylls and carotenes. Probably the most well-known carotenoid is the one that gives this group its name, carotene, found in carrots and responsible for their bright orange color. Molecules such as alpha-carotene, beta-carotene, lycopene and astaxanthin are also examples of un-oxidized carotenoids.
Polyphenolics molecules represent an important family of phytochemicals, comprising flavonoids, phenolic acids and non-flavonoid polyphenolics. Flavonoids have been associated with anti-allergic, anti-inflammatory, anti-microbial and anti-cancer activity. Proanthocyanins and quercentin represents the most important flavonoids in terms of therapeutic interest.
Glucosinolates are a class of phytochemicals that contain sulfur, nitrogen and a group derived from glucose. They occur as secondary metabolites of many plants. A known member of the glucosinolate family is sulforaphane which represents an anticancer compound found in broccoli.
Other known phytochemicals are thiosulfonates, phytosterols, anthraquinones, capsaicin, piperine, chlorophyll, betaine, pectin and oxalic acid.
Due to their anti-allergic, anti-inflammatory, anti-microbial and anti-cancer activity and potential use in treatment and/or prevention of cardiovascular diseases, there is a great interest in increasing phytochemicals concentration in fruits or vegetables and improving extraction techniques.
It would thus be highly desirable to be provided with effective means of achieving adequate conditioning of the biomass in order to produce high quality pellets and extracting maximum amount of phytochemicals from plant materials.